As semiconductor manufacturing technologies continue to evolve toward smaller design rules and higher integration densities (e.g., 14 nm technology node and beyond), integrated circuit devices and components become increasingly smaller, creating challenges in layout formation and device optimization. Currently, FinFET technologies are typically implemented for FET fabrication, as such technologies provide effective CMOS scaling solutions for FET fabrication at, and below, the 14 nm technology node. A FinFET device comprises a three-dimensional fin-shaped FET structure which includes at least one vertical semiconductor fin structure formed on a substrate, a gate structure formed over a portion of the vertical semiconductor fin, and source/drain regions formed from portions of the vertical semiconductor fin which extend from both sides of the gate structure. The portion of the vertical semiconductor fin that is covered by the gate structure between the source/drain regions comprises a channel region of the FinFET device.
The gate structures of FinFET devices can be formed using various techniques. For example, a FinFET gate structure can be fabricated using a “gate-last” process, which involves, for example, forming a dummy gate structure and a gate spacer over a portion of a vertical semiconductor fin, fabricating other FinFET device elements (e.g., source/drain regions), and then replacing the dummy gate structure with a metal gate structure using a replacement metal gate (RMG) process. For advanced FinFET technologies, it is important to prevent etch damage to the vertical semiconductor fins when etching a dielectric layer to form the gate spacers.
With conventional methods, a gate spacer is formed by depositing and patterning a layer of dielectric material using, e.g., RIE (reactive ion etching). Due to the limited selectivity of the RIE process, the vertical semiconductor fins can be subjected to significant etch damage when patterning the layer of dielectric material to form the gate spacers. While the spacer RIE process can be tuned to minimize etch erosion of vertical semiconductor fins formed of silicon (Si) or silicon-germanium (SiGe), the selectively of the RIE process decreases with the scaling of fin pitch (e.g., reducing inter fin spacing), and as the fin height increases (e.g., increasing aspect ratio for spacer RIE).